This invention relates to catalysts for olefin polymerisation, in particular to catalyst compounds containing metals xcex7-bonded by xcex75-ligands, e.g. cyclopentadienyl ligands and xcex7 or "sgr"-bonded by a bicyclic nitrogen ligand, and their use in olefin polymerisation.
In olefin polymerization, it has long been known to use as a catalyst system the combination of a metallocene procatalyst and an alumoxane or boron based co-catalyst.
By xe2x80x9cmetallocenexe2x80x9d is here meant an xcex7-ligand metal complex, e.g. an xe2x80x9copen sandwichxe2x80x9d or xe2x80x9chalf sandwichxe2x80x9d compound in which the metal is complexed by a single xcex7-ligand, a xe2x80x9csandwichxe2x80x9d compound in which the metal is complexed by two or more xcex7-ligands, a xe2x80x9chandcuffxe2x80x9d compoundxe2x80x9d in which the metal is complexed by a bridged bis-xcex7-ligand or a xe2x80x9cscorpionatexe2x80x9d compound in which the metal is complexed by an xcex7-ligand linked by a bridge to a "sgr"-ligand.
Metallocene procatalysts are generally used as part of a catalyst system which also includes an ionic cocatalyst or catalyst activator, for example, an aluminoxane (e.g. methylaluminoxane (MAO), hexaisobutylaluminoxane and tetraisobutylaluminoxane) or a boron compound (e.g. a fluoroboron compound such as triphenylpentafluoroboron or triphentylcarbenium tetraphenylpentafluoroborate ((C6H5)3B+Bxe2x88x92(C6F5)4) )
Alumoxanes are compounds with alternating aluminium and oxygen atoms generally compounds of formula 
where each R, which may be the same or different, is a C1-10 alkyl group, and p is an integer having a value between 0 and 40). These compounds may be prepared by reaction of an aluminium alkyl with water. The production and use of alumoxanes is described in the patent literature, especially the patent applications of Texas Alkyls, Albemarle, Ethyl, Phillips, Akzo Nobel, Exxon, Idemitsu Kosan, Witco, BASF and Mitsui.
Traditionally, the most widely used alumoxane is methylalumoxane (MAO), an alumoxane compound in which the R groups are methyls. MAO however is poorly characterised and relatively expensive and efforts have been made to use alumoxanes other than MAO. Thus, for example WO98/32775 (Borealis) proposes the use of metallocene procatalysts with alumoxanes in which R is a C2-10 alkyl group, eg hexaisobutylalumoxane (HIBAO). However, such metallocenes generally have poor catalyst activities with non-MAO alumoxanes.
Since each polymerisation catalyst gives rise to polymer products with slightly differing properties, there remains an ongoing search for new and improved olefin polymerisation catalysts.
We have now surprisingly found that a single site procatalyst system based on a xcex75-ligand, e.g. cyclopentadienyl type ligand and a xcex7 or "sgr"-bonding bicyclic nitrogen ligand may be used very effectively in polymerisation catalysis, especially in the manufacture of polyethylene or polypropylene.
Thus viewed from one aspect the invention provides a compound of formula (I) comprising 
wherein
LIG represents an xcex75-ligand substituted by a group R1 and a group (Rxe2x80x3)m;
X represents a 1 to 3 atom bridge, optionally substituted, e.g. by Rxe2x80x3 groups;
Y represents a nitrogen or phosphorus atom;
Z represents a carbon, silicon, nitrogen or phosphorus atom;
the ring denoted by A1 is an optionally substituted, optionally saturated or unsaturated 5 to 12 membered heterocyclic ring;
the ring denoted by A2 is an optionally substituted, unsaturated 5 to 12 membered heterocyclic ring;
R1 represents hydrogen, Rxe2x80x3 or a group OSiRxe2x80x23;
each Rxe2x80x2, which may be the same or different is a R+, OR+, SR+, NR+2 or PR+2 group where each R+ is a C1-16 hydrocarbyl group, a tri-C1-8 hydrocarbylsilyl group or a tri-C1-8hydrocarbylsiloxy group, preferably Rxe2x80x2 being a C1-12 hydrocarbyl group, e.g. a C1-8 alkyl or alkenyl group;
each Rxe2x80x3, which may be the same or different is a ring substituent which does not form a "sgr"-bond to a metal xcex7-bonded by the bicyclic ring, eg it may be hydrogen, R+, OR+, SR+, NR+2 or PR+2 group where each R+ is a C1-16 hydrocarbyl group, a tri-C1-8 hydrocarbylsilyl group or a tri-C1-8hydrocarbylsiloxy group; and
m is zero or an integer between 1 and 3.
Viewed from a further aspect the invention provides an olefin polymerisation catalyst system comprising or produced by reaction of (1) a metallated compound as hereinbefore defined (from hereon called a procatalyst) and (2) a cocatalyst, e.g. an aluminium alkyl compound or boron compound, in particular an alumoxane, especially an aluminium alkyl compound comprising alkyl groups containing at least two carbon atoms.
Viewed from a still further aspect the invention provides a process for olefin polymerisation comprising polymerising an olefin in the presence of a catalyst system as hereinbefore described.
Viewed from a yet further aspect the invention provides a process for the preparation of a procatalyst, said process comprising metallating with a group 3 to 7 transition metal a compound of formula (I) 
wherein LIG, X, Y, Z and rings A1 and A2 are as hereinbefore defined.
Viewed from a further aspect the invention provides the use of a procatalyst as hereinbefore defined in olefin polymerization, especially ethylene or propylene polymerisation or copolymerisation.
Viewed from a yet further aspect the invention provides an olefin polymer produced by a polymerisation catalysed by a procatalyst compound as hereinbefore defined.
The compounds of formula (I) as hereinbefore described may be coupled with a metal from groups 3 to 7. By group 3 (etc) metal is meant a metal in group 3 of the Periodic Table of the Elements, namely Sc, Y, etc. It is preferable if the metal coupling the compound of the invention is in the III+ oxidation state, although metals in the II+ and IV+ oxidation states are also advantageous. The metal employed in the catalyst system of the invention is most preferably from groups 4, 5 or 6 of the periodic table, e.g. Cr, Mo, W, Ti, Zr, Hf, V, Nb or Ta. Most especially the metal is Cr or Ti, e.g. Cr3+ or Ti3+.
Where the metal is Cr, it has surprisingly been found that the catalyst system of the invention is capable of making polypropylene as a powder.
The group 3 to 7 metal in the metallated procatalyst of the invention coordinates to the xcex75-ligand and "sgr" or xcex7 bonds to certain atoms in the bicyclic nitrogen ligand. Where the metal forms sigma bonds with the bicyclic nitrogen ligand, only atoms Z and N can coordinate to the metal. Thus, the metal may be coordinated only to atom X, only to N or to both the Z and N atoms. The Y atom is therefore not involved in coordination with the metal.
However, if an xcex7 ligand is formed between the metal and bicyclic nitrogen group then coordination to any double bond present in bicyclic nitrogen ligand is possible. Such xcex7 bonds may be xcex72 or xcex73 depending on the nature of the bicyclic nitrogen ligand. The metal may also be coordinated by hydrogen atoms, hydrocarbyl "sgr"-ligands (eg optionally substituted C1-12 hydrocarbyl groups, such as C1-12 alkyl, alkenyl or alkynyl groups optionally substituted by fluorine and/or aryl (eg phenyl) groups), by silane groups (eg Si(CH3)3), by halogen atoms (eg chlorine), by C1-8 hydrocarbylheteroatom groups, by tri-C1-8hydrocarbylsilyl groups, by bridged bis-"sgr"-liganding groups, by amine (eg N(CH3)2) or imine (eg Nxe2x95x90C or Nxe2x95x90P groups, eg (iPr)3Pxe2x95x90N) groups, or by other "sgr"-ligands known for use in metallocene (pro) catalysts.
By a "sgr"-ligand moiety is meant a group bonded to the metal at one or more places via a single atom, eg a hydrogen, halogen, silicon, carbon, oxygen, sulphur or nitrogen atom.
Examples of "sgr"-ligands include
halogenides (e.g. chloride and fluoride), hydrogen,
triC1-12 hydrocarbyl-silyl or -siloxy(e.g. trimethylsilyl),
triC1-6 hydrocarbylphosphimido (e.g. triisopropylphosphimido),
C1-12hydrocarbyl or hydrocarbyloxy (e.g. methyl, ethyl, phenyl, benzyl and methoxy),
diC1-6 hydrocarbylamido (e.g. dimethylamido and diethylamido), and
5 to 7 ring membered heterocyclyl (eg pyrrolyl, furanyl and pyrrolidinyl). Preferable "sgr" ligands include halogens, alkyls, or chloro-amido groups.
Y preferably represents a nitrogen atom.
In the catalyst system formed from the compound of the invention, the Y atom does not sigma coordinate to the metal ion. Instead, the atom at Y serves to provide an atom whereby the bridging group X can join the bicyclic nitrogen group to the xcex75-ligand.
The Z atom, which as mentioned above may be involved in coordination with the metal ion, is preferably a phosphorus or nitrogen atom, especially a nitrogen atom.
In a most preferred embodiment both Y and Z are nitrogen.
The A rings (A1 and A2), formed partially from the atoms xe2x80x94Yxe2x80x94Cxe2x80x94Zxe2x80x94 or xe2x80x94Nxe2x80x94Cxe2x80x94Zxe2x80x94 may be or different sizes but are preferably or the same size. Moreover, each ring preferably has either 5 or 6 members. Whilst the rings may contain further heteroatoms selected from N, P, S or B, this is not preferred. Thus, apart from the potential heteroatoms represented by Y and Z, the A rings are preferably formed from carbon atoms. The A rings may contain double bonds and may be aromatic but preferably the rings contain no double bonds in addition to the double bond which must be present between the C and N in formula (I). Preferably, the rings are unsubstitued.
Thus suitable bicyclic groups include those illustrated below. 
In a highly preferred embodiment the bicyclic group is formed from two fused six membered rings and Y and Z are nitrogen, i.e. the last or the five structures above.
The xcex75-ligand may be any xcex75-ligand which forms an xcex7-bond with the complexing metal ion. Suitable ligands therefore include dipyridylmethanyl, indenyl, fluorenyl or cyclopentadienyl ligands. The xcex75-ligand is substituted by groups R1 and (Rxe2x80x3)m as hereinbefore defined. Hence, suitable procatalysts or use in the invention include those of formula 
wherein R1, Rxe2x80x3, m, X, Y, Z and rings A1 and A2 are as hereinbefore defined. Alternatively, the xcex75-ligand is of formula 
wherein R1, Rxe2x80x3, m, X, Y, Z and rings A1 and A2 are as hereinbefore defined. In the above formula, the R1 and Rxe2x80x3 groups may be bound to any ring of the xcex75-ligand, i.e. although the R1 group in the formula immediately above is depicted as being generally present on the 5-membered ring, the nomenclature is intended to cover the possibility or the R1 group being present on the 6-membered ring.
The preferred nature of the groups R1 and Rxe2x80x3 varies depending on the nature or the xcex75-ligand. Where the xcex75-ligand is a cyclopentadienyl, R1 is preferably a group of formula OSiRxe2x80x23. Preferably Rxe2x80x2 is a C1-12 hydrocarbyl group, e.g. a C1-18 alkyl or alkenyl group, especially methyl or isopropyl.
Examples of suitable Rxe2x80x23SiO groups in the compounds or procatalysts of the invention include 
Where the xcex75-ligand is a cyclopentadienyl group, the OSiRxe2x80x23 group may be situated at any position on the cyclopentadienyl ring but preferably is alpha to the carbon atom involved in bridging.
The cyclopentadienyl group itself may be substituted by up to three groups Rxe2x80x3 and Rxe2x80x3 preferably represents C1-16 alkyl, especially methyl. In a highly preferred embodiment, three Rxe2x80x3 groups are present and Rxe2x80x3 is methyl. Since R1 may also represent Rxe2x80x3 a cyclopentadienyl substituted by four methyl groups is also within the scope of the invention.
Also within the scope of the invention are cyclopentadienyl groups wherein one of the carbon atoms not bound to the bridging group X or if present the OSiRxe2x80x23 group, is replaced by a heteroatom selected from phosphorus, silicon, nitrogen or boron. It is stressed however, that preferably there are no heteratoms present in the cyclopentadienyl ring.
Thus typical examples or suitable cyclopentadienyl type moieties include: 
Examples of particular cyclopentadienyl siloxy groups usable according to the invention include:
triisopropylsiloxycyclopentadienyl,
1-triisopropylsiloxy-3-methyl-cyclopentadienyl,
1-triisopropylsiloxy-3,4-dimethyl-cyclopentadienyl,
1-triisopropylsiloxy-2,3,4-trimethyl-cyclopentadienyl,
(dimethyltertbutylsiloxy)-cyclopentadienyl,
1-(dimethyltertbutylsiloxy)-3-methylycyclopentadienyl,
1-(dimethyltertbutylsiloxy)-3,4-dimethylcyclopentadienyl,
1-(dimethyltertbutylsiloxy)-2,3,4-trimethyl-cyclopentadienyl,
1-triisopropylsiloxy-2-phospholyl,
1-triisopropylsiloxy-3-phospholyl,
1-dimethyltertbutylsiloxy-2-phospholyl,
1-dimethyltertbutylsiloxy-3-phospholyl,
1-triisopropylsiloxy-2-borolyl,
1-triisopropylsiloxy-3-borolyl,
1-dimethyltertbutylsiloxy-2-borolyl,
1-dimethyltertbutylsiloxy-3-borolyl,
1-(dimethyloct-1-en-8-ylsiloxy)-3-methyl-cyclopentadienyl,
1-(dimethyloct-1-en-8-ylsiloxy)-3,4-dimethyl-cyclopentadienyl.
Where the xcex75-ligand is a dipyridylmethanyl, indenyl or fluorenyl species the R1 may also be a group of formula OSiRxe2x80x23 as hereinbefore described but preferably R1 is hydrogen. Rxe2x80x3 may represent a C1-6 alkyl, especially methyl but again in a preferred embodiment Rxe2x80x3 is hydrogen. Where the xcex7 ligand is indenyl, Rxe2x80x3 may preferably represent an n-alkenyl, e.g. n-hexyl.
Examples of particular further xcex7-ligands are well known from the technical and patent literature relating to metallocene olefin polymerization catalysts, e.g. EP-A-35242 (BASF), EP-A-129368 (Exxon), EP-A-206794 (Exxon), PCT/FI97/00049 (Borealis), EP-A-318048, EP-A-643084, EP-A-69951, EP-A-410734, EP-A-128045, EP-B-35242 (BASF), EP-B-129368 (Exxon), WO97/23493, Organometallics 1995, 14, 471 and EP-B-206794 (Exxon). Further suitable xcex7-ligands are those or formula 
The bridging group X is preferably a one or two atom bridge comprising silicon or carbon. The bridge preferably connects to a carbon atom present in the 5-membered ring or the xcex75-ligand. However, where the ligand comprises a heteroatom such as boron, the bridge may attach to the heteroatom or to the heteroatom""s substituents. Where the bridge is formed from silicon, the bridge may be of formula xe2x80x94Si(R2)2 wherein each R2 independently represents a C1-10 alkyl, C1-10 alkenyl, aryl, e.g. phenyl, trimethylsilyl, or both R2 groups taken together may form a ring, e.g. five membered ring, with the Si. Where the bridge comprises carbon, the bridge is preferably a one atom bridge, e.g. xe2x80x94CH2xe2x80x94 or xe2x80x94CH(CH3)2xe2x80x94. Suitable bridges are depicted below 
In a highly preferred embodiment, compound according to the invention is of formula 
wherein Rxe2x80x2, m and Rxe2x80x3 are as hereinbefore described.
Further typical examples of the procatalysts or the invention include: 
The procatalysts of the invention may be prepared by conventional techniques which will be readily devised by the person skilled in the art. Conveniently for example, the procatalyst is constructed by combining the bicyclic ligand with, for example, the siloxy cyclopentadienyl ligand followed by subsequent metallation. The bridging group may be carried by either the bicyclic ligand or the cyclopentadienyl ligand but conveniently the bridging group is attached to the bicyclic group first.
Where the bicyclic group is for example 1.5.7-triaza[4.4.0]bicyclo-dec-5-ene this may be deprotonated by a strong base and the resulting anion reacted with a bridging group such as dimethylsilyldichloride. The cyclopentadienyl xcex7-ligands used according to the invention may be prepared by reaction of a corresponding siloxycyclopentadiene with an organolithium compound, eg methyllithium or butyllithium. The reaction or the lithium cyclopentadienyl species with the bicyclic ligand carrying bridiging group gives rise to a compound or the invention after further deprotonation. These reactions are depicted in the Scheme below. 
Fluorenyl and indenyl compounds of the invention may be prepared by analogous techniques to those required to prepare the cyclopentadienyl compounds.
Where the xcex7-ligand is a dipyridylmethanediyl, the bicyclic nitrogen ligand may be reacted with a species generated as illustrated in the following scheme. 
Deprotonation of the product again leaves the compound of the invention. The starting material may be functionalised as necessary to have required substituents using conventional synthetic chemistry. It is of course possible to have the dipyridylmethanediyl carry the bridging group using the following chemistry: 
The compound can be metallated conventionally, eg by reaction with a halide or the metal M, preferably in an organic solvent, eg a hydrocarbon or a hydrocarbon/ether mixture.
"sgr"-ligands other than chlorine may be introduced by displacement or chlorine from an xcex7-ligand metal chloride by reaction with appropriate nucleophilic reagent (e.g. methyl lithium or methylmagnesium chloride) or using, instead or a metal halide, a reagent such as tetrakisdimethylamidotitanium or metal compounds with mixed chloro and dimethylamido ligands.
As mentioned above, the olefin polymerisation catalyst system of the invention comprises (i) a procatalyst formed from a metallated compound of formula (I) and (ii) an aluminium alkyl compound, or the reaction product thereof. While the aluminium alkyl compound may be an aluminium trialkyl (eg triethylaluminium (TEA)) or an aluminium dialkyl halide (eg diethyl aluminium chloride (DEAC)), it is preferably an alumoxane, particularly an alumoxane other than MAO, most preferably an isobutylalumoxane, eg TIBAO (tetraisobutylalumoxane) or HIBAO (hexaisobutylalumoxane). Alternatively however the alkylated (eg methylated) metallocene procatalysts of the invention (e.g. compounds or formula V wherein Z is alkyl) may be used with other cocatalysts, eg boron compounds such as B(C6F5)3, C6H5N(CH3)2H:B(C6F5)4, (C6H5)3C:B(C6F5)4 or Ni (CN)4[B(C6F5)3]42xe2x80x94.
The metallocene procatalyst and cocatalyst may be introduced into the polymerization reactor separately or together or, more preferably they are pre-reacted and their reaction product is introduced into the polymerization reactor.
If desired the procatalyst, procatalyst/cocatalyst mixture or a procatalyst/cocatalyst reaction product may be used in unsupported form or it may be precipitated and used as such. However the metallocene procatalyst or its reaction product with the cocatalyst is preferably introduced into the polymerization reactor in supported form, eg impregnated into a porous particulate support.
The particulate support material used is preferably an organic or inorganic material, e.g. a polymer(such as for example polyethylene, polypropylene, an ethylene-propylene copolymer, another polyolefin or polystyrene or a combination thereof). Such polymeric supports may be formed by precipitating a polymer or by a prepolymerization, eg of monomers used in the polymerization for which the catalyst is intended. However, the support is especially preferably a metal or pseudo metal oxide such as silica, alumina or zirconia or a mixed oxide such as silica-alumina, in particular silica, alumina or silica-alumina. Particularly preferably, the support material is acidic, e.g. having an acidity greater than or equal to silica, more preferably greater than or equal to silica-alumina and even more preferably greater than or equal to alumina. The acidity of the support material can be studied and compared using the TPD (temperature programmed desorption or gas) method. Generally the gas used will be ammonia. The more acidic the support, the higher will be its capacity to adsorb ammonia gas. After being saturated with ammonia, the sample or support material is heated in a controlled fashion and the quantity of ammonia desorbed is measured as a function of temperature.
Especially preferably the support is a porous material so that the metallocene may be loaded into the pores of the support, e.g. using a process analogous to those described in WO94/14856 (Mobil), WO95/12622 (Borealis) and WO96/00243 (Exxon). The particle size is not critical but is preferably in the range 5 to 200 xcexcm, more preferably 20 to 80 xcexcm.
Before loading, the particulate support material is preferably calcined, ie heat treated, preferably under a non-reactive gas such as nitrogen. This treatment is preferably at a temperature in excess or 100xc2x0 C., more preferably 200xc2x0 C. or higher, e.g. 200-800xc2x0 C., particularly about 300xc2x0 C. The calcination treatment is preferably effected for several hours, e.g. 2 to 30 hours, more preferably about 10 hours.
The support may be treated with an alkylating agent before being loaded with the metallocene. Treatment with the alkylating agent may be effected using an alkylating agent in a gas or liquid phase, e.g. in an organic solvent for the alkylating agent. The alkylating agent may be any agent capable of introducing alkyl groups, preferably C1-16 alkyl groups and most especially preferably methyl groups. Such agents are well known in the field of synthetic organic chemistry. Preferably the alkylating agent is an organometallic compound, especially an organoaluminium compound (such as trimethylaluminium (TMA), dimethyl aluminium chloride, triethylaluminium) or a compound such as methyl lithium, dimethyl magnesium, triethylboron, etc.
The quantity of alkylating agent used will depend upon the number of active sites on the surface of the carrier. Thus for example, for a silica support, surface hydroxyls are capable of reacting with the alkylating agent. In general, an excess of alkylating agent is preferably used with any unreacted alkylating agent subsequently being washed away.
Where an organoaluminium alkylating agent is used, this is preferably used in a quantity sufficient to provide a loading of at least 0.1 mmol Al/g carrier, especially at least 0.5 mmol Al/g, more especially at least 0.7 mmol Al/g, more preferably at least 1.4 mmol Al/g carrier, and still more preferably 2 to 3 mmol Al/g carrier. Where the surface area of the carrier is particularly high, lower aluminium loadings may be used. Thus for example particularly preferred aluminium loadings with a surface area of 300-400 m2/g carrier may range from 0.5 to 3 mmol Al/g carrier while at surface areas of 700-800 m2/g carrier the particularly preferred range will be lower.
Following treatment of the support material with the alkylating agent, the support is preferably removed from the treatment fluid and any excess treatment fluid is allowed to drain off.
The optionally alkylated support material is loaded with the procatalyst, preferably using a solution of the procatalyst in an organic solvent therefor, e.g. as described in the patent publications referred to above. Preferably, the volume of procatalyst solution used is from 50 to 500% or the pore volume of the carrier, more especially preferably 80 to 120%. The concentration of procatalyst compound in the solution used can vary from dilute to saturated depending on the amount of metallocene active sites that it is desired be loaded into the carrier pores.
The active metal (ie. the metal or the procatalyst) is preferably loaded onto the support material at from 0.1 to 4%, preferably 0.5 to 3.0%, especially 1.0 to 2.0%, by weight metal relative to the dry weight of the support material.
After loading of the procatalyst onto the support material, the loaded support may be recovered for use in olefin polymerization, e.g. by separation of any excess procatalyst solution and if desired drying or the loaded support, optionally at elevated temperatures, e.g. 25 to 80xc2x0 C.
Alternatively, a cocatalyst, e.g. an alumoxane or an ionic catalyst activator (such as a boron or aluminium compound, especially a fluoroborate) may also be mixed with or loaded onto the catalyst support material. This may be done subsequently or more preferably simultaneously to loading of the procatalyst, for example by including the cocatalyst in the solution of the procatalyst or, by contacting the procatalyst loaded support material with a solution of the cocatalyst or catalyst activator, e.g. a solution in an organic solvent. Alternatively however any such further material may be added to the procatalyst loaded support material in the polymerization reactor or shortly before dosing of the catalyst material into the reactor.
In this regard, as an alternative to an alumoxane it may be preferred to use a fluoroborate catalyst activator, especially a B(C6F5)3 or more especially a xe2x8ax96B(C6F5)4 compound, such as C6H5N(CH3)2H:B(C6F5)4 or (C6H5)3C:B(C6F5)4. Other borates or general formula (cation+)a (boratexe2x88x92)b where a and b are positive numbers, may also be used.
Where such a cocatalyst or catalyst activator is used, it is preferably used in a mole ratio to the metallocene of from 0.1:1 to 10000:1, especially 1:1 to 50:1, particularly 1:2 to 30:1. More particularly, where an alumoxane cocatalyst is used, then for an unsupported catalyst the aluminium:metallocene metal (M) molar ratio is conveniently 2:1 to 10000:1, preferably 50:1 to 1000:1. Where the catalyst is supported the Al:M molar ratio is conveniently 2:1 to 10000:1 preferably 50:1 to 400:1. Where a borane cocatalyst (catalyst activator) is used, the B:M molar ratio is conveniently 2:1 to 1:2, preferably 9:10 to 10:9, especially 1:1. When a neutral triarylboron type cocatalyst is used the B:M molar ratio is typically 1:2 to 500:1, however some aluminium alkyl would normally also be used. When using ionic tetraaryl borate compounds, it is preferred to use carbonium rather than ammonium counterions or to use B:M molar ratio below 1:1.
Where the further material is loaded onto the procatalyst loaded support material, the support may be recovered and if desired dried before use in olefin polymerization.
The olefin polymerized in the method or the invention is preferably ethylene or an alpha-olefin or a mixture or ethylene and an xcex1-olefin or a mixture of alpha olefins, for example C2-20 olefins, e.g. ethylene, propene, n-but-l-ene, n-hex-l-ene, 4-methyl-pent-l-ene, n-oct-l-ene-etc. The olefins polymerized in the method of the invention may include any compound which includes unsaturated polymerizable groups. Thus for example unsaturated compounds, such as C6-20 olefins (including cyclic and polycyclic olefins (e.g. norbornene)), and polyenes, especially C6-20 dienes, may be included in a comonomer mixture with lower olefins, e.g. C2-5 xcex1-olefins. Diolefins (ie. dienes) are suitably used for introducing long chain branching into the resultant polymer. Examples of such dienes include xcex1,xcfx89 linear dienes such as 1,5-hexadiene, 1,6-heptadiene, 1,8-nonadiene, 1,9-decadiene, etc.
In general, where the polymer being produced is a homopolymer it will preferably be polyethylene or polypropylene. Where the polymer being produced is a copolymer it will likewise preferably be an ethylene or propylene copolymer with ethylene or propylene making up the major proportion (by number and more preferably by weight) or the monomer residues. Comonomers, such as C4-6 alkenes, will generally be incorporated to contribute to the mechanical strength or the polymer product.
Usually metallocene catalysts yield relatively narrow molecular weight distribution polymers; however, if desired, the nature or the monomer/monomer mixture and the polymerization conditions may be changed during the polymerization process so as to produce a broad bimodal or multimodal molecular weight distribution (MWD) in the final polymer product. In such a broad MWD product, the higher molecular weight component contributes to the strength or the end product while the lower molecular weight component contributes to the processability of the product, e.g. enabling the product to be used in extrusion and blow moulding processes, for example for the preparation of tubes, pipes, containers, etc.
A multimodal MWD can be produced using a catalyst material with two or more different types of active polymerization sites, e.g. with one such site provided by the metallocene on the support and further sites being provided by further catalysts, e.g. Ziegler catalysts, other metallocenes, etc. included in the catalyst material.
Polymerization in the method of the invention may be effected in one or more, e.g. 1, 2 or 3, polymerization reactors, using conventional polymerization techniques, e.g. gas phase, solution phase, slurry or bulk polymerization.
In general, a combination of slurry (or bulk) and at least one gas phase reactor is often preferred, particularly with the reactor order being slurry (or bulk) then one or more gas phase.
For slurry reactors, the reaction temperature will generally be in the range 60 to 110xc2x0 C. (e.g. 85-110xc2x0 C.), the reactor pressure will generally be in the range 5 to 80 bar (e.g. 50-65 bar), and the residence time will generally be in the range 0.3 to 5 hours (e.g. 0.5 to 2 hours). The diluent used will generally be an aliphatic hydrocarbon having a boiling point in the range xe2x88x9270 to +100xc2x0 C. In such reactors, polymerization may if desired be effected under supercritical conditions.
For gas phase reactors, the reaction temperature used will generally be in the range 60 to 115xc2x0 C. (e.g. 70 to 110xc2x0 C.), the reactor pressure will generally be in the range 10 to 25 bar, and the residence time will generally be 1 to 8 hours. The gas used will commonly be a non-reactive gas such as nitrogen together with monomer(e.g. ethylene).
For solution phase reactors, the reaction temperature used will generally be in the range 130 to 270xc2x0 C., the reactor pressure will generally be in the range 20 to 400 bar and the residence time will generally be in the range 0.1 to 1 hour. The solvent used will commonly be a hydrocarbon with a boiling point in the range 80-200xc2x0 C.
Generally the quantity of catalyst used will depend upon the nature or the catalyst, the reactor types and conditions and the properties desired for the polymer product. Conventional catalyst quantities, such as described in the publications referred to herein, may be used.
All publications referred to herein are hereby incorporated by reference.
General Considerations
All operations were carried out in argon or nitrogen atmosphere using standard Schlenk, vacuum and dry box techniques. Solvents were dried with potassium benzophenone ketyl and distilled under argon prior to use. 1.5.7-triaza[4.4.0]bicyclo-dec-5-ene (TAB-H) (Fluka) and dipyridylketone (DPM-H) (Fluka) were used as purchased. Benzyl potassium was prepared according to Schlosser, M. and Hartmann, J. Angew. Chem 1973, 85, 544-545. CrCl3(THF)3 and TiCl3(THF)3 were prepared according to W. A. Herrmann and G. Brauer, Synthetic Methods or Organometallic and Inorganic Chemistry, Vol. 1: Literature, Laboratory Techniques and Common Starting Materials, Thieme 1996. 1H- and 13C-NMR spectra were recorded using JEOL JNM-EX 270 MHz FT NMR spectrometer with tetramethylsilane (TMS) as an internal reference. 13C-CPMAS NMR and the mass spectra were recorded at Fortum Oil and Gas Oy, Analytical Research department. The CPMAS-NMR spectra were recorded using Chemagnetics Infinity 270 MHz equipment and the direct inlet MS spectra were produced by VG TRIO 2 quadrupole mass spectrometer in electron impact ionisation mode (EIMS) (70 eV). The GC-MS analyses were performed using Hewlett Packard 6890/5973 Mass Selective Detector in electron impact ionisation mode (70 eV) equipped with a silica capillary column (30 mxc3x970.25 mm i.d.). The FTIR spectra were recorded at Borealis Analytical Research department using Perkin-Elmer Spectrum 2000 spectrometer with inert diamond ATR accessory and 4 cm-1 resolution. Thermogravic measurements (TG) were recorded using GWB METTLER TG50 Termobalance and the Differential Scanning Calorimetry (DSC) and melting point analyses using GWB METTLER DSC-30 under inert conditions at Borealis Analytical Research department. The polymerization tests were carried out using MAO, 30% solution in toluene purhased from Albermarle. Test polymerizations were carried out in pentane at 60xc2x0 C. and at 80xc2x0 C. with hydrogen present using an Al/M ratio or 1000 unless otherwise stated. A Bxc3xcchi 2 L stirred reactor with mantle heating was used for the polymerization tests.